Deputy Prime Minister Nick Clegg was tonight facing a Commons revolt by Liberal Democrat MPs over the Government's controversial NHS reforms.
Five Lib Dem backbenchers have tabled an amendment to Labour's opposition day motion on the Health and Social Care Bill calling on the House to "decline to support" the legislation "in its current form".
The amendment instead calls on the Government to hold an "urgent summit" with the royal colleges, professional bodies and patients' organisations to plan health reforms for England "based on the coalition agreement".
Labour welcomed the move and said that it offered a last chance to block the bill before it completes its passage through Parliament next week.
The tabling of the amendment comes after Lib Dem activists refused to back the bill at their spring conference in Gateshead.
Greg Mulholland, one of the Lib Dem signatories to the amendment, said that the Government should now accept that it needed to re-think its reform plan.
"The bill should now be pulled and interested parties and colleagues should come together and plan reform of the health service, in line with the collation agreement, instead of pushing ahead with these reforms," he wrote on his website.
"Pushing a bill through in any area, never mind in one so important as the NHS, with so many professional organisations and medical professionals opposed is not a sensible or acceptable way to make policy and it is time to get people round the table and find a different and acceptable way forward."
With Labour sources signalling they would support the Lib Dem rebel amendment, shadow health secretary Andy Burnham said it was not too late to block the legislation.
"Labour is clear that we can still stop it," he said.
"We have a new opportunity to develop an agreement between Labour and the Liberal Democrats on the NHS bill. Patients who depend on the NHS and staff who have devoted their lives to it want to see political parties find common ground."
A Lib Dem spokesman said: "The Lib Dems have changed this bill in a thousand ways and our conference at the weekend recognised that success.
"As a result, this is a much better bill, which makes competition the servant not the master of the NHS and secures long-standing Liberal Democrat objectives around democratic accountability and putting patients before profits."
A Downing Street spokeswoman said: "We are still committed to the Bill. We need to modernise the NHS and look forward to the Bill becoming law."
Asked about the Royal College of General Practioners' call for talks on the implementation of the reforms, she said Number 10 was "disappointed" about its continued opposition to the reform proposals.
"We are keen to engage with all those organisations who are constructively working with us to improve the NHS," the spokeswoman said.
Asked whether that included the Royal College, she added: "They continue to oppose the Bill."